1. Technical Field
The present invention relates to a liquid ejecting head including a piezoelectric element that causes a change in pressure in a pressure-generating chamber communicating with a nozzle opening and has a piezoelectric layer and electrodes for applying a pressure to the piezoelectric layer, and relates to a liquid ejecting apparatus and a piezoelectric element.
2. Related Art
In some of piezoelectric elements used in liquid ejecting heads, the piezoelectric element has a structure in which a piezoelectric layer made of a piezoelectric material exhibiting an electromechanical conversion function such as a crystallized dielectric material is disposed between two electrodes. Such a piezoelectric element is mounted on a liquid ejecting head as a flexure-vibration-mode actuator. A typical example of the liquid ejecting head is an ink jet recording head in which a diaphragm configures a part of a pressure-generating chamber communicating with a nozzle opening for discharging ink droplets and a pressure is applied to the ink in the pressure-generating chamber by deforming the diaphragm by a piezoelectric element to discharge the ink as droplets from the nozzle opening.
The piezoelectric material used for the piezoelectric element is required to have high piezoelectric properties, and their typical examples include lead zirconate titanate (PZT) (see JP-A-2001-223404).
However, from the viewpoint of an environmental problem, there is a demand for a piezoelectric material having a less content of lead. As an example of the piezoelectric material not containing lead, a potassium sodium niobate-based piezoelectric material has been proposed (see JP-A-2009-10367). The potassium sodium niobate-based material has high piezoelectric properties and a high Curie temperature Tc, which is therefore useful as a lead-free piezoelectric material.
Unfortunately, crack occurs easily to the potassium sodium niobate-based piezoelectric layers during the preparation process. Especially in case of making thick piezoelectric layers, crack problem becomes more serious.
Such a problem occurs not only in ink jet recording heads, but also in other liquid ejecting heads for discharging droplets other than ink. In addition, the problem occurs in piezoelectric elements that are used for devices other than liquid ejecting heads.